Beta-damascenone is an aroma factor in the distillation aerosol of cured tobacco. It has a typical fruity and cooked apple flavor, which can also be found naturally in Rosa damascena Mill (the Damask rose), thereby indicating the existence of an enzymatic pathway leading to its synthesis in some plants. The flowers of Rosa damascena are renowned for their fine fragrance, and are commercially harvested for rose oil used in perfumery and to make rose water. The flower petals are also sometimes used directly to flavor food or drink and are considered safe for human consumption.
Carotenoids are potential precursors for beta-damascenone production. Thermal oxidation of neoxanthin leads to the formation of beta-damascenone. Neoxanthin is an oxygenated carotenoid derivative belonging to the class of xanthophylls and consists of eight isoprenoid units. In senescent and cured leaves, free neoxanthin is not present or is only detected at very low levels. Within the plant carotenoid pathway which occurs in the plastids—such as chloroplasts—enzymes known to form neoxanthin belong to the class of neoxanthin synthases. Neoxanthin synthase catalyses the formation of neoxanthin from violaxanthin and is encoded by the ABA4 polynucleotide. Lycopene beta cyclase also catalyses the formation of neoxanthin from violaxanthin and is encoded by the NeSy polynucleotide. 9-cis-epoxycarotenoid dioxygenase(s) catalyses the cleavage of cis-neoxanthin in C25-allenic-apo-aldehyde and xanothin and is encoded by the NCED2 polynucleotide.
There is a continuing need in the art for plant materials—such as tobacco—with modified flavour profiles. It is an object of the present invention to satisfy this need.